Throughout the entire encounter, mechanical contraptions spawn in waves of two. They target a random player in the chamber and detonate, AEing a DD spell coupled with a stun. They can only be killed via the Disarm Trap ability (and only after they've done their emote).

After you kill the 3rd clockwork Nurtha will not spawn as a corpse, it will spawn as a mob, at low health, you have to beat off a few % before you get the chest/loot, and door to unlock, so be rdy for that.